1. Field of the Invention
The present invention relates to a unitary molded front cover lens filter for a touch screen interface with an associated process control device. In particular, the present invention incorporates a front cover that provides a watertight seal for a sensing control device, especially against bursts of high pressure water, while enabling operator input through a sensor adjacent a display screen. Known art may be found in U.S. Class 345, subclass 175 as well as in other classes and subclasses.
2. Description of the Prior Art
Many types of automated control systems, computer controlled systems and hybrids thereof have evolved through the years to dominate the manufacturing and processing industries in this country. Such systems have literally revolutionized industrial production and increased the speed and productivity of the average worker in this country.
One common type of these computer systems permits an operator to interactively control manufacturing and/or industrial and/or other processes by entering information into the computer during such processes to thereby control the process. Some interactive systems facilitate this operator control by permitting the operator to evaluate status information shown on a display screen, such as a cathode ray tube or liquid crystal display or any other associated display device, and then selectively touching points on the screen to interact with the system. Such interactive systems have become increasingly prevalent in most major food processing plants.
An example of a common interactive touch input system is one that provides an arrangement of radiation or infrared emitters and corresponding detectors in pairs. That is, a line of infrared light emitters are usually arranged along two adjacent sides (i.e. one vertically and the other horizontally abutting) along the outer periphery of the display screen with the other line of detectors arranged oppositely. Other types of sensors are available as well including acoustic and optical that work similarly.
This arrangement of emitters and corresponding detectors produces a grid of light over the screen. When an operator intersects the grid by inserting their finger or another object therein to penetrate the light grid, the computer subsequently determines the grid location of the intersection. Of course, the computer could be replaced by hard-wired display electronics or the like. Once an intersection is detected, the grid intersection information is correlated to a control algorithm with subsequent process activity.
This sophisticated control system is in widespread use and it has proven resilient in most environments. However, a problem has arisen with respect to the use of such systems in the exceptionally harsh operating environments, for example those of large food processing plants and particularly plants processing poultry and the like. These automated control systems are subject to various foreign objects including the processed food items, grease, moisture, corrosive contaminants, and liquids including especially water and harsh cleaning solutions.
As will be appreciated by those skilled in the art, contamination of the display and/or display cover is particularly a problem in computer systems that use touch input. The operator constantly touches the device during normal operations and many such touches are not soft as they often occur during situations where speed of control and adjustment to the process are critical and operator stress is correspondingly elevated.
Moreover, in the food processing industries, the processing equipment including the sensor control screens are cleaned regularly, normally on a daily basis. Such cleaning often subjects the touch screen to prolonged exposure to various cleaning fluids, liquids and/or solutions. The cleaning fluids can cause additional reactions with the display elements. Even more destructive is the use of high pressure water/cleaning fluid solutions directly upon the display element including all of its periphery.
As can be imagined, a permanent liquid tight seal is required to shield the internal sensitive electronic display elements from exposure and destruction by these forces.
Prior art techniques have attempted to solve this problem in several ways. Multiple gaskets between the lens filter and the machine cover and housing have been attempted to address the leakage problem. However, even multiple gaskets can leak after exposure to harsh cleaning fluids and the additional assembly steps required for extra gaskets can be time-consuming. The use of multiple gaskets can also require multiple operations and parts which can make front covers using such gaskets more expensive to manufacture. Exposed gaskets also can leak after a relatively short period of time due to the expansion and contraction of the gasket itself due to temperature changes in the environment and exposure of the gasket material to the harsh cleaning chemicals and high pressure cleaning solutions normally used in food processing plants.
Another attempted solution involves using a transparent polycarbonate material. Such material is fused to a plastic cover by injection molding and then mechanically mated with a glass or other transparent material as the rear viewscreen. These devices are subject to failure in the hash operating environments of food processing plants as well. Varying thermal expansion and contraction rates for the various components causes them to eventually warp and distort or crack. Consequently, a watertight seal is often impossible to maintain and fluid penetration of the cover invariably occurs.
Thus, a need exists for an improved, unitary lens for a touch sensing device that effectively resists short bursts of high pressure cleaning solutions, harsh chemicals and caustic conditions while maintaining a sufficient level of protection for sensitive internal components.